The present invention relates to a gear arrangement, and more particularly to a gear arrangement in which backlash between two gears meshed with each other is eliminated.
In a gear transmission arrangement, backlash is intentionally provided between gear faces taking into consideration a machining error of gears and a manufacturing error in a distance between axes of gears. However, because of this backlash, a gear arrangement is liable to generate noises during its operation, and for instance, in the case where a rotational speed of a gear on a driving side varies or its direction of rotation changes, knocking sounds are generated.
For the purpose of eliminating the backlash, a counter-measure was taken in the prior art, for example, such that a gear on a driving side and a gear on a driven side are meshed with each other while providing backlash therebetween, around a shaft of either one gear, for instance, the gear on the driven side is loosely fitted a gear of the same size as the one gear, and these two gears are made to repel each other in the circumferential direction by means of a spring to make the loosely fitted gear also mesh with the gear on the driving side. Since the above-described two gears on the driven side mesh with the tooth on the driving side on the tooth faces on the opposite side to each other, if the strength of the spring is chosen so as to overcome a transmission torque, knocking noises would not be generated even when a direction of rotation changes.
In addition, in Japanese Utility Model Publication No. 48-44543 is disclosed a gear arrangement, in which backlash is eliminated by employing such structure that teeth of one of meshing gears can move a little in the radial direction with respect to a shaft of the one gear by interposing an elastic body or a frictional body such as a rubber, a spring or the like between the teeth and the shaft of the one gear and, by mounting these two gears with the distance between their shafts somewhat shortened as compared to a normal mounting distance.
However, as to the gear arrangement in which two gears made to repel each other in the circumferential direction by means of a spring are meshed with one gear on the opposite side as described above, a necessary number of gear becomes large, also the mechanism becomes complex, and hence the cost of the gear arrangement would become high.
Furthermore, with regard to the backlash eliminating means disclosed in Japanese Utility Model Publication No. 48-44543, since the distance between the shafts of the two gears must be shortened, in the case where it is intended to change a gear arrangement in the prior art to this gear arrangement incorporating the backlash eliminating means, the positions of bearings must be also changed. Especially in the case of a gear arrangement associated with an engine, positions of bearing holes on an engine block must be changed, and therefore, change of machining jigs would accompany therewith, so that many problems are involved.